Shawn Conley and John Gaska, Dept of Agronomy, reported on the potential for reduced soybean seed quality this year and their concern for planting in cool wet soils. This article is just a quick reminder that seedcorn maggot may also be a contributing factor.  Seedcorn maggot injury is often more severe during a cool/wet growing season and soybean are more susceptible to maggot injury than corn. Unless we are out looking for symptoms soon after emergence damage is often undiagnosed leaving people to assume that poor seed quality, compaction, disease, etc were the reasons for low stand counts. 

In previous articles it has been mentioned that seedcorn maggot injury can be greater after manure applications or when green manure is incorporated. Also, recently tilled field may also be attractive to ovipositing females and damage can be confined to a narrow window of planting dates. Dig up areas with poor emergence and inspect seed for damage to confirm seedcorn maggot injury. Above ground symptoms may include light to severe brown feeding scars on the cotyledons which can delay soybean development but usually doesn’t result in yield loss if the growing point is unaffected. If the hypocotyl is severed below the growing point symptoms called “snakehead” will form because the remaining hypocotyl elongates for a short period of time then bends near the point of injury. The unifoliates may also have a few holes from seedcorn maggot feeding but this injury is usually not of economic concern. 

Image 1: Seedcorn Maggot injury to seed